SwiftUI is a mobile focused framework still being adapted to macOS, I think it’s just gotten tables this year? And even the best Catalyst app in the world (craft.do) will sit somewhere in between Electron and uncanny valley at times when it comes to things as simple as a button.
I would highly recommend using AppKit if the app is even slightly nontrivial and fit and finish is a goal.
If it’s a simple app and you’re ok with visual hitches and oddities but would like a native macOS “skin”, SwiftUI.
If fit and finish isn’t important, just use Electron.
Only one thing to add: Embrace the fact that Swift and Objective C are compatible! Some parts are way easier to write in Objective C, eg. anything that interfaces with C code.
Also, if your app does non-trivial amounts of text editing, those parts should probably be written in Objective C.
Working with NSTextView / NSString / NSMutableString / NSAttributedString in Swift is difficult. You always need to be super careful not to mix up Objective C characters (UTF-16) with Swift characters ("Grapheme clusters"). Even as someone who read a lot about those topics it's easy to mix them up. It's also easy to run into catastrophic performance problems, eg. checking large strings for equality is really slow in Swift, and can easily lead to UI hangs.
I gave up using Storyboards a long time ago.
Mac Catalyst is the current probable best way, but is looking long in tooth as SwiftUI gets all the love
AppKit is the old way but unless you want to relearn a bunch I wouldn't recommend it
For most applications, I'd suggest SwiftUI. That's because most UIs are for straightforward CRUD apps. Because everyone else here makes great points. There are lots of reasons to avoid SwiftUI at the moment.
However, I've made a handful of SwiftUI apps for macOS that were more than simple. It works well.
